Specific Heat and Scaling of 4He Confined in a Planar Geometry

We report measurements of the specific heat of thick helium films to test scaling predictions near the superfluid transition, Tλ. These films, bounded by two silicon wafers, range in thickness from 0.107 to 0.692μm. The specific heat of the films is suppressed relative to that of bulk helium, and the difference of the data from bulk helium scales well with the exponent of the correlation length. We propose an empirical scaling function which fits the data well for T>Tλ, and yields the surface specific heat. We also compare the data with various theoretical calculations and experiments. We find that the calculations underestimate the effect of confinement. copyright 1997 The American Physical Society